1. Field of the Invention
The present invention resides in lubrication compositions having extreme pressure and anti-wear properties, which are suitable for use as a replacement for sulfurized sperm oil in many lubrication applications.
Recently, over harvesting of sperm whales and their diminishing population has resulted in the inclusion of this species of whale in the United States in the "Endangered Species Conservation Act of 1969". Similarly, a ban went into effect on imports of oil, meat and other products of sperm and seven other species of whale in December 1970 in the United States. The unique liquid wax produced by sperm whales is of importance in various extreme pressure lubricant applications, for example, as tractor hydraulic fluids, automotive gear lubricants, industrial gear lubricants, and automotive transmission fluids. Sperm oil has additionally been sulfonated, oxidized, sulfurized, sulfur-chlorinated, and chlorinated to give products that have use in industry as wetting agents and extreme pressure additives.
Extreme pressure or "E.P." additives, as they are commonly called, are chemicals which are added to lubrication compositions to prevent destructive metal-to-metal contact in the lubrication of moving surfaces. Lubrication oils provide good lubrication between moving surfaces in contact with each other, as long as a film of said oil is maintained between the relative moving surfaces. This particular kind of lubrication is commonly termed "hydrodynamic". However, when pressures or rubbing speeds between moving metal surfaces are such that the film of lubrication oil is wiped or squeezed out, metal-to-metal contact and wear occurs over a significant portion of the lubricated area. Under such conditions, a kind of lubrication called boundary lubrication is needed, and is governed by parameters of the contacting surfaces, for example, surface finish, metal shear strength, and the coefficient of friction between the metals involved. Destructive metal-to-metal contact, due to lack of lubrication under extreme conditions, manifests itself in different forms such as scoring, welding, scuffing, ridging, rippling, and in some cases deformation or complete destruction of the lubrication component.
Extreme pressure and anti-wear lubricating additives prevent destructive metal-to-metal contact, under boundary lubrication conditions, by reacting with relatively moving metal surfaces to form an adherent film of metallic salts which has a lower shear strength than that of the metal surfaces. This film acts in the capacity of a "solid lubricant" and performs the function of lubrication when metal-to-metal contact occurs.
Extreme pressure and anti-wear lubricant additives are characterized by no appreciable formation of "solid lubricant" on the metal surface under hydrodynamic lubrication conditions and a formation of said "solid lubricant" only at the elevated temperatures which develop between the moving metal surfaces under conditions of boundary lubrication.
Research in the area to develop a substitute for sperm oil has taken two approaches. The first involves replacement of the sperm oil derivative with similar chemicals derived from other raw materials that have performance properties equivalent to its sperm oil counterpart. The second approach involves disregarding the chemical nature of sperm oil derivatives and formulating products or compounds that provide equivalent performance properties. However, the unusual combination of composition and properties of sperm oil have made the search for a replacement a difficult one. Thus, a lubrication composition is highly desirable that either matches or surpasses sperm oil as a lubricant.
We have discovered that sulfurized diesters comprising the condensation product of a dicarboxylic acid or a dicarboxylic acid anhydride and a linear unsaturated alcohol, preferably in combination with a minor amount of sulfurized unsaturated alcohol, are suitable for use as a substitute or replacement for sperm oil and its derivatives in extreme pressure and anti-wear lubrication applications.
2. Description of the Prior Art
The use of diesters as a sperm oil substitute is known and appreciated by the prior art. For example, U.S. Pat. No. 3,850,827, entitled "Sperm Oil Substitute From Blend of Carboxylic Acid Esters of Glycols," issued to Zipf, on Nov. 26, 1974, discloses a liquid lubricant comprising a blend of mono and diesters of an organic glycol, for example, ethylene glycol, and a monocarboxylic acid, for example, saturated acids such as capric and unsaturated acids such as oleic, etc. The above diesters can additionally be sulfurized or undergo sulfation to impart desirable characteristics to the compositions.
U.S. Pat. No. 2,802,024, entitled "Diesters of Oxo Glycols," issued to Fasce et al, on Aug. 6, 1957, relates to synthetic lubricating compositions and a method of preparation. Particularly, the reference teaches the preparation of dibasic acid centered complex esters by reacting an oxo glycol with a monobasic acid to form the half ester and reacting the half ester thus formed with a dibasic acid. Similarly, simple diesters are prepared by reacting a glycol with a monobasic acid to form a diester. The diesters thus produced are said to be suitable for use as synthetic lubricants.
Other synthetic lubricants are disclosed in U.S. Pat. No. 3,637,500, entitled "Lubricating Compositions", issued to Forbes et al, on January 25, 1972. Specifically, the reference relates to diesters having a central alkylene group having 1 to 25 carbon atoms, carboxyl groups on either side of the central alkylene group and alkyl groups having from 1 to 10 carbon atoms attached to the carboxyl groups. These diesters are used in combination with disulfides in lubricating compositions, for example, mineral base oils, as synthetic lubricants which are said to increase the load-carrying properties of the base oil.
U.S. Pat. No. 3,919,187, entitled "Sulfur-Containing Compositions of Unsaturated Esters, Their Use as Additives for Lubricating Compositions Containing Them," issued to Bourdoncle et al, on November 11, 1975, relates to lubricating compositions comprising a mineral or synthetic oil in combination with a sulfurized ester consisting of an aliphatic mono- or di- carboxylic acid with at least one aliphatic ethylenically unsaturated monohydric alcohol. The sulfurized diesters are described as suitable substitutes for sulfurized spermaceti oil.
Lubricant compositions are additionally set forth in U.S. Pat. No. 3,875,069, entitled, "Lubricant Compositions Useful in the Shaping of Thermoplastic Materials," issued to Worschech et al, on Apr. 1, 1975, discloses lubricant compositions consisting of mixed esters of aliphatic polyols, dicarboxylic acids and long-chained aliphatic monocarboxylic acids in combination with a second group of esters selected from esters of dicarboxylic acids and long-chained aliphatic alcohols; long-chained aliphatic monocarboxylic acids and long-chained aliphatic alcohols; and complete or partial esters of monocarboxylic acids and aliphatic polyols.
From the foregoing, it can be seen there is an ongoing search for extreme pressure, anti-wear lubrication compositions which are suitable substitutes for sulfurized sperm oil.